Biomechanics

Accelerometry for outdoor effort quantification

Assessing the lower limb properties in-situ is of a major interest for analyzing the athletic performance. From a physical point of view, the lower limb could be modeled as single linear spring which supports the whole body mass. The main mechanical parameter studied when using this spring-mass-model is the leg-spring stiffness (k). In laboratory conditions, the movements are assessed using a force plate (Meth1) which measures the ground reaction force (GRF), and a motion capture system which could estimate the displacement of the centre of mass (CoM). In this way, k is calculated as shown in equation (2).More recent methods allow to calculate k in field conditions by using either foot switches (Meth2) or accelerometry-based instruments (Meth3) which are both wireless devices. The associated calculated methods assume that force-time signal is a sine wave, described by the equation (3) with equation (4) (CT: contact time; FT: flight time). In these cases, the kinematic measurement (CoM) could be calculated either by a mathematical approach (Eq.(5)) (meth2), or by double integrating the acceleration (meth3) in order to calculate k.Thanks to their transportability, the methods 2 and 3 offer not only the possibility to assess the lower limb movements, but also, to objectively follow up the athletic abilities (performance, reactivity, force and power, stiffness) in-situ.


Listed In: Biomechanical Engineering, Biomechanics, Sports Science


Effects of cortical stimulation on sensorimotor hand functions in healthy elderly individuals

Transcranial anodal stimulation (tDCS) improves manual dexterity in healthy old adults. The underlying changes in finger force behavior for this improved dexterity have not been reported. Here, we investigated the effects of tDCS (20-min) over primary motor cortex (M1) combined with repeated practice on the Grooved pegboard test (tDCS+MP) on the fingertip forces applied to an object during grasp and manipulation. Eight right-handed able-bodied individuals (60-85 years) participated in a sham-controlled, single-blinded study. Each participant received anodal and sham intervention in two sessions at least 5-day apart. Before and after intervention, they performed a ‘key-slot’ task that required inserting a slot on an object onto a stationary bar, an isometric force production task using a pinch grip, and the Grooved pegboard test. Anodal relative to sham tDCS+MP allowed participants to better retain the improved performance on the pegboard test. For the isometric task, anodal tDCS+MP significantly increased the variability of force compared to sham tDCS+MP. More importantly, the improved retention of performance post-anodal tDCS correlated with the reduction in force angle variability on the key-slot task, but not with the change in force variability on the isometric task. Our findings suggest that anodal tDCS+MP facilitated retention of learning on a skillful manual task in healthy old adults, consistent with the role of M1 in retention of learning versus skill acquisition. Furthermore, improved force steadiness is one of the potential mechanisms through which short-term anodal tDCS during motor training yields improved performance on a functional task.
Listed In: Biomechanics, Neuroscience


HIP JOINT TORQUES DURING A GOLF SWING AFTER A TOTAL HIP REPLACEMENT: A CASE SERIES

Purpose: Total Hip Replacements (THR) are common procedures for older people who suffer from degenerative joint disease. Golf is a popular leisure sport played by older Americans including those with THR. Hip torques encountered in a golf swing after THR has not been reported. The purpose of this study is to describe 3D hip joint torques generated during a golf swinging by those with THR. Methods: Three male amateur golfers who were at least 1 year post THR (ages 59-71 year old and right hand dominant, (2 were left THR) participated. Golf handicap ranged from 16-18. All participants completed the Hip Harris Score. Passive reflective markers were placed on key boney anatomical landmarks. During data collection, participants completed ten swings using a standardized driver, after a warm up. Kinetics and kinematics were captured using a 10 camera Motion Analysis system and two AMTI forceplates. Inverse dynamics procedure was used to calculate peak hip torques in all three planes. Hip torques were normalized and presented as internal torques. Comparisons were made to previously collected similarly aged senior group. Results: Average Club head velocity was slower than senior group. Sagittal Plane: THR golfers exhibited the greatest torque similar to senior group. Frontal plane: THR golfers demonstrated a lower hip adductor torque on the lead leg compared to the trail leg and senior group. Transverse plane: THR exhibited higher hip external rotation torques compared to the internal rotation torques and the senior group. Conclusion: 3-D peak hip torques generated during the golf swing by persons with a THR are greatest in the sagittal plane. THR golfers demonstrated slower club head speed but generated higher hip torques in the transverse plane as compared to those without a THR. Hip external rotation torque was higher in all of the THR compared to the senior group. Clinical Significance: Subjects with a THR may be prone to abnormal forces in the transverse plane during the golf swing. Future studies are needed to determine impact on return to golf decisions following a THR.
Listed In: Biomechanics, Physical Therapy, Sports Science